Currently, there is a huge demand for high data-rate and bandwidth-efficient wireless transmission standards (such as 802.11 Wireless LAN, cellular LTE, and 5G) due to extensive use of wireless communication in various fields of applications, such as in homes, public places, or office areas. Accordingly, various concepts, such as linear amplification using nonlinear components (LINC) (also known as outphasing), are being used for highly efficient linear power amplification of wireless signals, for example RF signals.
Typically, in an outphasing transmit wireless system, an RF signal with varying amplitude (also referred to as “variable-envelope signal”) may be decomposed into two (or more) components with constant amplitude and different phases (also referred to as “constant-envelope signals”). Such constant envelope signals may be amplified by power amplifiers in an RF transmitter.
In certain scenarios, the RF transmitter may further include a power combiner that may combine the two amplified constant-envelope signals. The combined signal may be then transmitted by the RF transmitter, via a multi-antenna array, to an RF receiver. In certain instances, when the power combiner is an isolating power combiner, such as a Wilkinson combiner, a certain amount of power may be lost in a resistor within the power combiner due to the different phases of the two outphasing constant-envelope signals. Alternatively, when the power combiner is a non-isolating (low-loss) power combiner, the power amplifiers that feed the power combiner may interfere with each other. Such interference may reduce the linearity of the power amplifiers and hence, may increase the error vector magnitude (EVM) of the RF signal. Thus, there is required a low-loss isolating outphasing power combiner that overcomes these deficiencies.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present disclosure as set forth in the remainder of the present application with reference to the drawings.